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https://dev.mysql.com/doc/refman/8.0/en/index-extensions.html
InnoDB automatically extends each secondary index by appending the primary key columns to it. Consider this table definition: CREATE TABLE t1 ( i1 INT NOT NULL DEFAULT 0, i2 INT NOT NULL DEFAULT 0, d DATE DEFAULT NULL, PRIMARY KEY (i1, i2), INDEX ...It also defines a secondary index k_d on column (d), but internally InnoDB extends this index and treats it as columns (d, i1, ...
https://dev.mysql.com/doc/refman/8.0/en/select-optimization.html
Queries, in the form of SELECT statements, perform all the lookup operations in the database. NDB Cluster supports a join pushdown optimization whereby a qualifying join is sent in its entirety to NDB Cluster data nodes, where it can be distributed ...Tuning these statements is a top priority, whether to achieve sub-second response times for dynamic web pages, or to chop hours off the time to generate huge overnight ...
https://dev.mysql.com/doc/refman/8.0/en/constraints.html
We must handle the case when you have inserted or updated a lot of rows in a nontransactional table for which changes cannot be rolled back when an error occurs. Several SQL mode options are available to provide greater control over handling of bad ...The basic philosophy is that MySQL Server tries to produce an error for anything that it can detect while parsing a statement to be executed, and tries to recover from any errors that occur while executing the ...
https://dev.mysql.com/doc/refman/8.0/en/partitioning-limitations-partitioning-keys-unique-keys.html
The rule governing this relationship can be expressed as follows: All columns used in the partitioning expression for a partitioned table must be part of every unique key that the table may have. In other words, every unique key on the table must ...
https://dev.mysql.com/doc/refman/8.0/en/descending-indexes.html
For InnoDB full-text search, this means that the index required on the FTS_DOC_ID column of the indexed table cannot be defined as a descending index. Descending indexes also make it possible for the optimizer to use multiple-column indexes when the ... MySQL supports descending indexes: DESC in an index definition is no longer ignored but causes storage of key values in descending ...
https://dev.mysql.com/doc/refman/8.0/en/get-diagnostics.html
If that is not the case, a GET STACKED DIAGNOSTICS when handler not active error occurs. This instance of GET DIAGNOSTICS assigns the SQLSTATE value and error message to the user variables @p3 and @p4: GET DIAGNOSTICS CONDITION 1 @p3 = ...(You can ... GET [CURRENT | STACKED] DIAGNOSTICS { statement_information_item [, statement_information_item] ...
https://dev.mysql.com/doc/refman/8.0/en/invisible-indexes.html
If an index made invisible actually is needed or used by the optimizer, there are several ways to notice the effect of its absence on queries for the table: Errors occur for queries that include index hints that refer to the invisible index. MySQL ...Dropping and re-adding an index can be expensive for a large table, whereas making it invisible and visible are fast, in-place ...
https://dev.mysql.com/doc/refman/8.0/en/sys-schema-prerequisites.html
Before using the sys schema, the prerequisites described in this section must be satisfied. Because the sys schema provides an alternative means of accessing the Performance Schema, the Performance Schema must be enabled for the sys schema to work.
https://dev.mysql.com/doc/refman/8.0/en/compiler-characteristics.html
In some cases, the compiler used to build MySQL affects the features available for use. The notes in this section apply for binary distributions provided by Oracle Corporation or that you compile yourself from source. icc (Intel C++ Compiler) ...
https://dev.mysql.com/doc/refman/8.0/en/multiple-tables.html
Given these considerations, the CREATE TABLE statement for the event table might look like this: mysql> CREATE TABLE event (name VARCHAR(20), date DATE, type VARCHAR(15), remark VARCHAR(255)); As with the pet table, it is easiest to load the initial ... The pet table keeps track of which pets you ...An event type ...